1. Field of the Invention
The present invention relates to an illumination optical system for enlarging an image displayed on image display means such as a liquid crystal display panel or micromirror device panel and projecting thus enlarged image onto a screen, and a projector apparatus using the same; and, in particular, to an illumination optical system in which the relative positional relationship between an integrator section for homogenizing the illumination of light illuminating the image display means and other optical members is improved, and a projector apparatus using the same.
2. Description of the Prior Art
In illumination optical systems for liquid crystal projectors, there has conventionally been known a technique using an optical system which employs an integrator for eliminating unevenness in illumination on liquid crystal display panels.
Namely, such an illumination optical system comprises a first integrator plate (generally known as second flyeye or the like), a second integrator plate (generally known as first flyeye or the like), and a condenser lens successively disposed in this order downstream a light source section using a reflector. The first integrator plate is constituted by a plurality of lens elements, each having a form substantially analogous to that of a liquid crystal display panel, which are arranged two-dimensionally, and splits a luminous flux having a relatively higher degree of unevenness in brightness emitted from the light source section into partial luminous fluxes by the number identical to that of the lens elements in the first integrator plate. Thus obtained partial luminous flux has a lower degree of unevenness in brightness as compared with the luminous flux before being split. By means of the second integrator plate and the condenser lens, the individual partial luminous fluxes are emitted toward an area to be illuminated, so as to be superposed on one another, whereby it is possible to realize illumination with less unevenness in brightness.
Meanwhile, since the projection lens employed in a liquid crystal projector is often used as being shifted in a direction perpendicular to the optical axis of its liquid crystal display panel, it is generally designed such that its liquid crystal side is formed into a telecentric system. Also, in conjunction therewith, the illumination optical system using an integrator is generally designed as a system in which the luminous flux becomes telecentric after passing through the liquid crystal display panel. When such a telecentric system is formed, however, it may be problematic in that a large number of lenses are needed as the projection lens, each lens has a larger diameter, and so forth, thereby increasing the size and cost of the apparatus.
Therefore, a so-called non-telecentric system in which the luminous flux does not become telecentric after passing through the liquid crystal display panel may be constructed. However, in the case where a conventional illumination optical system employing an integrator used in a liquid crystal projector is disposed so as to be inclined as a whole with respect to the liquid crystal display panel, it becomes necessary to newly design support members for individual members of the illumination optical system, a housing for accommodating the illumination optical system, and the like, whereby such a change may not always be easy.
As image display means, attention has recently been given to the micromirror device panel (DMD) in which a plurality of micromirror devices are arranged. In the micromirror device panel, it is necessary that a luminous flux be made obliquely incident thereon while forming a predetermined angle with the normal of the panel. Therefore, in the case where such a micromirror device panel is used as the image display means, it is difficult to simply use the illumination optical system mounted in the conventional liquid crystal projector.